1. Field of the Invention
The present invention relates to an ink supply for an ink-jet printer and, more particularly to a replaceable ink supply having a self-contained pump that can be actuated to supply ink from a reservoir within the ink supply to a print head within the inkjet printer.
2. Description of Related Art
A typical ink-jet printer has a print head mounted to a carriage which is moved back and forth over a printing surface, such as a piece of paper. As the print head passes over appropriate locations on the printing surface, a control system activates ink jets on the print head to eject, or jet, ink drops onto the printing surface and form desired images and characters.
To work properly, such printers must have a reliable supply of ink for the print head. Many ink-jet printers use a disposable ink pen that can be mounted to the carriage. Such an ink pen typically includes, in addition to the print head, a reservoir containing a supply of ink. The ink pen also typically includes pressure regulating mechanisms to maintain the ink supply at an appropriate pressure for use by the print head. When the ink supply is exhausted, the ink pen is disposed of and a new ink pen is installed. This system provides an easy, user friendly way of providing an ink supply for an ink-jet printer.
However, in a printer using an ink pen, the entire ink pen, including the reservoir and ink supply, is moved with the print head. This requires a trade-off. If the ink pen has a large reservoir and ink supply, it is heavier and is more difficult to move quickly. This may limit the speed with which the printer can print--an important characteristic of a printer. On the other hand, if the ink pen has a small reservoir and ink supply, it will be depleted more quickly and require more frequent replacement.
The problems posed by size limitations of the ink reservoir have been heightened by the increasing popularity of color printers. In a color printer, it is usually necessary to supply more than one color of ink to the print head. Commonly, three or four different ink colors, each of which must be contained in a separate reservoir, are required. The combined volume of all of these reservoirs is limited in the same manner as the single reservoir of a typical one-color printer. Thus, each reservoir can be only a fraction of the size of a typical reservoir for a one-color printer.
Furthermore, when even one of the reservoirs is depleted, the ink pen may no longer be able to print as intended. Thus, the ink pen must typically be replaced and discarded when the first of the reservoirs is exhausted. This further decreases the useful life of the ink pen.
As can be appreciated, the print head and pressure regulating mechanism of the ink pen contribute substantially to the cost of the ink pen. These mechanisms can also have a useful life expectancy far longer than the supply of ink in the reservoir. Thus, when the ink pen is discarded, the print head and pressure regulating mechanisms may have a great deal of usable life remaining. In addition, in multiple color ink pens, it is unlikely that all of the ink reservoirs will be depleted at the same time. Thus, the discarded ink pen will likely contain unused ink as well as a fully functional print head and pressure regulating mechanism. This results in increased cost to the user and a somewhat wasteful and inefficient use of resources.
To alleviate some of the shortcomings of disposable ink pens, some ink-jet printers have used ink supplies that are not mounted to the carriage. Such ink supplies, because they are stationary within the printer, are not subject to all of the size limitations of an ink supply that is moved with the carriage. Some printers with stationary ink supplies have a refillable ink reservoir built into the printer. Ink is supplied from the reservoir to the print head through a tube which trails from the print head. Alternatively, the print head can include a small ink reservoir that is periodically replenished by moving the print head to a filling station at the stationary, built-in reservoir. In either alternative, ink may be supplied from the reservoir to the print head by either a pump within the printer or by gravity flow.
However, such built-in reservoirs are frequently difficult and messy to refill. In addition, because they are never replaced, built-in ink reservoirs tend to collect particles and contaminants that can adversely affect printer performance.
In view of these problems, some printers use replaceable reservoirs. These reservoirs, like the built-in reservoirs are not located on the carriage and, thus, are not moved with the print head during printing. Replaceable reservoirs are often plastic bags filled with ink. The bag is provided with a mechanism, such as a septum which can be punctured by a hollow needle, for coupling it to the printer so that ink may flow from the bag to the print head. Often, the bag is squeezed, or pressurized in some other manner, to cause the ink to flow from the reservoir. Should the bag burst or leak while under pressure, the consequences can be catastrophic for the printer.